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A098685
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Numbers n such that pi(n)=sigma(d_1)*sigma(d_2)*...*sigma(d_k) where d_1 d_2 ... d_k is the decimal expansion of n.
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3
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15, 155, 252, 916, 1189, 12654, 55293, 177554, 418634, 753248, 885193, 18252678, 18252687, 18469156, 18469165, 19882616, 19882623, 41867246, 73526936, 73526957, 233843449, 244895519, 2345784285, 2399877831, 4273447776
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Next term is greater than 10000000.
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EXAMPLE
| 885193 is in the sequence because pi(885193)= sigma(8)*sigma(8)*sigma(5)*sigma(1)*sigma(9)*sigma(3).
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MATHEMATICA
| Do[d=IntegerDigits[n]; k=Length[d]; If[ !MemberQ[d, 0]&&PrimePi[n]== Product[DivisorSigma[1, d[[j]]], {j, k}], Print[n]], {n, 10000000}]
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CROSSREFS
| Cf. A098686, A098683, A098684.
Sequence in context: A010035 A017389 A157380 * A006096 A099915 A110557
Adjacent sequences: A098682 A098683 A098684 * A098686 A098687 A098688
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KEYWORD
| base,nonn
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AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Sep 24 2004
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EXTENSIONS
| a(12)-a(25) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jun 18 2009
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